This relates to a device for releasably securing abrasive disks to a backing plate which is adapted for rotational movement activated by a grinder. It is particularly useful for rapid release attachment of such abrasive disks.
In an industrial environment, especially one involving a moving production line, it is important that tools be available for use with minimum delays. Unfortunately abrasive disks wear out and need to be replaced. As a result there have been developed many quick-change devices for abrasive disks such as disks with a pressure sensitive adhesive backing which are carried on a smooth rubber backup pad and backup pads with one component of a hook and loop attachment mechanism with the other half attached to the abrasive disk.
Where the disk is more substantial and heavier it is more convenient to have the disk mechanically attached to the backup pad. One such device, which is sold by the Merit Company, requires a specially adapted backup pad, and comprises a plastic element glued to the side of the disk opposed to the abrasive bearing side. The element comprises a number of teeth projections which cooperate with apertures in the backup pad such that, when the teeth are inserted in the corresponding apertures and the disk is rotated, the teeth are retained in the apertures, thus retaining the disk on the backup pad. Such an approach is effective unless the disk is larger than about 5 inches and is subject to fairly heavy pressure during grinding. In this event the strain imposed on the adhesive junction between the plastic element and the disk is too great and can easily fail.
In another commercially available device, an abrasive disk is provided with a plate clamped to the abrasive-bearing surface and having two metal tongues projecting from the reverse side of the plate and beyond the back surface of the disk. The tongues have a portion of increased thickness. These tongues project into slots in an annular groove in a backing plate that is shaped to provide increased frictional contact with the tongues as the rotation increases. This is achieved by providing matching inclined surfaces on the tongues and an internal surface of the groove such that the tongue portion of increased thickness is retained in a rebate in the groove surface and the frictional pressure between the tongue and the groove surface with which it is in contact increases with rotation of the disk relative to the backing plate. This construction is quite effective but it places a substantial metal anchoring plate on the abrasive surface of the abrasive disk. This is not a problem when the disk is intended for use at a angle of about 45.degree. or more to a workpiece and only the outer rim of the abrasive disk is actually used to abrade a workpiece. However for disks intended for use at a lower, flatter angle to a workpiece, the risk of contact of the metal anchoring plate with the workpiece becomes significant. In addition the rotational forces generated in use fall upon the two projecting tongues which therefore need to be very sturdy. Since these are stamped from he same piece of metal, this in turn dictates the thickness of the anchoring plate.
There is therefore a need for a quick-release, positive retention device for securing a heavy duty abrasive disk to a backup pad that can be used with abrasive disks that are designed to be used at a much flatter grinding angle than is currently used. This need is supplied by the present invention which provides a disk retention device that is able to withstand very high torque conditions without failing while remaining readily attachable and detachable with little effort.